telegraf/plugins/inputs/system/DISK_README.md

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# Disk Input Plugin
The disk input plugin gathers metrics about disk usage.
Note that `used_percent` is calculated by doing `used / (used + free)`, _not_
`used / total`, which is how the unix `df` command does it. See
https://en.wikipedia.org/wiki/Df_(Unix) for more details.
### Configuration:
```
# Read metrics about disk usage by mount point
[[inputs.disk]]
# By default, telegraf gather stats for all mountpoints.
# Setting mountpoints will restrict the stats to the specified mountpoints.
# mount_points = ["/"]
```
Additionally, the behavior of resolving the `mount_points` can be configured by using the `HOST_MOUNT_PREFIX` environment variable.
When present, this variable is prepended to the mountpoints discovered by the plugin before retrieving stats.
The prefix is stripped from the reported `path` in the measurement.
This settings is useful when running `telegraf` inside a docker container to report host machine metrics.
In this case, the host's root volume should be mounted into the container and the `HOST_MOUNT_PREFIX` and `HOST_ETC` environment variables set.
`docker run -v /:/hostfs:ro -e HOST_MOUNT_PREFIX=/hostfs -e HOST_ETC=/hostfs/etc telegraf-docker`
### Measurements & Fields:
- disk
- free (integer, bytes)
- total (integer, bytes)
- used (integer, bytes)
- used_percent (float, percent)
- inodes_free (integer, files)
- inodes_total (integer, files)
- inodes_used (integer, files)
### Tags:
- All measurements have the following tags:
- fstype (filesystem type)
- path (mount point path)
### Example Output:
```
% ./telegraf -config ~/ws/telegraf.conf -input-filter disk -test
* Plugin: disk, Collection 1
> disk,fstype=hfs,path=/ free=398407520256i,inodes_free=97267461i,inodes_total=121847806i,inodes_used=24580345i,total=499088621568i,used=100418957312i,used_percent=20.131039916242397 1453832006274071563
> disk,fstype=devfs,path=/dev free=0i,inodes_free=0i,inodes_total=628i,inodes_used=628i,total=185856i,used=185856i,used_percent=100 1453832006274137913
> disk,fstype=autofs,path=/net free=0i,inodes_free=0i,inodes_total=0i,inodes_used=0i,total=0i,used=0i,used_percent=0 1453832006274157077
> disk,fstype=autofs,path=/home free=0i,inodes_free=0i,inodes_total=0i,inodes_used=0i,total=0i,used=0i,used_percent=0 1453832006274169688
```